Diguanidinium bis­(μ-2-hydroxy­propane-1,2,3-tricarboxyl­ato)bis­[diaqua­zincate(II)] dihydrate

Al-Dajani, M.T.M.; Abdallah, H.H.; Mohamed, N.; Yeap, C.S.; Fun, H.-K.

doi:10.1107/S1600536809054439

metal-organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 66| Part 2| February 2010| Pages m109-m110

https://doi.org/10.1107/S1600536809054439

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Diguanidinium bis(μ-2-hydroxypropane-1,2,3-tricarboxylato)bis[diaquazincate(II)] dihydrate

Mohammad T. M. Al-Dajani,^a Hassan H. Abdallah,^b Nornisah Mohamed,^a ‡ Chin Sing Yeap ^c § and Hoong-Kun Fun ^c ^*¶

^aSchool of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, ^bSchool of Chemical Sciences, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^cX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 7 December 2009; accepted 17 December 2009; online 9 January 2010)

The asymmetric unit of the title compound, (CH₆N₃)₂[Zn₂(C₆H₅O₇)₂(H₂O)₂]·2H₂O, contains one-half of a centrosymmetric dizinc(II) complex anion, one guanidinium cation and one water molecule. Each Zn^II ion is hexacoordinated by two citrate anions, one in a bidentate fashion and the second monodentate, and two water molecules in a distorted octahedral geometry. Intramolecular O—H⋯O hydrogen bonds add further stability to the molecular structure. In the crystal structure, molecules are linked into a three-dimensional framework by intermolecular N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds.

Related literature

For general background to guanidine and citric acid, see: Raczyńska et al. (2003 ); Yamada et al. (2009 ); Sigman et al. (1993 ); Schuck (1934 ); Sherman et al. (1936 ). For applications of citric acid in industry and materials science, see: Blair et al. (1991 ); Jiang et al. (2007 ). For related guanidinium structures, see: Al-Dajani et al. (2009a ,b ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ).

Experimental

Crystal data

(CH₆N₃)₂[Zn₂(C₆H₅O₇)₂(H₂O)₂]·2H₂O
M_r = 737.21
Monoclinic, C 2/c
a = 28.9405 (4) Å
b = 8.5708 (1) Å
c = 11.3395 (2) Å
β = 95.249 (1)°
V = 2800.89 (7) Å³
Z = 4
Mo Kα radiation
μ = 1.81 mm⁻¹
T = 296 K
0.32 × 0.30 × 0.18 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ) T_min = 0.593, T_max = 0.734
32332 measured reflections
7693 independent reflections
5495 reflections with I > 2σ(I)
R_int = 0.026

Refinement

R[F² > 2σ(F²)] = 0.031
wR(F²) = 0.084
S = 1.05
7693 reflections
190 parameters
H-atom parameters constrained
Δρ_max = 0.45 e Å⁻³
Δρ_min = −0.29 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H1O3⋯O6	0.91	1.87	2.6445 (13)	142
N1—H1N1⋯O1W	0.86	2.38	3.1607 (19)	150
N1—H2N1⋯O4	0.92	2.10	2.9855 (17)	161
N2—H1N2⋯O5ⁱ	0.88	2.12	2.9351 (18)	154
N2—H2N2⋯O1Wⁱⁱ	0.88	2.05	2.9077 (19)	166
N3—H1N3⋯O4ⁱ	0.86	2.29	3.1011 (18)	156
N3—H1N3⋯O5ⁱ	0.86	2.55	3.3221 (18)	150
N3—H2N3⋯O1	0.85	2.36	3.1788 (18)	162
O1W—H1W1⋯O2ⁱⁱⁱ	0.80	1.97	2.7640 (15)	177
O1W—H2W1⋯O5^iv	0.82	2.05	2.8568 (17)	170
O2W—H1W2⋯O1ⁱⁱⁱ	0.84	1.88	2.7172 (12)	171
O2W—H2W2⋯O7^v	0.76	1.86	2.6116 (13)	167
O3W—H1W3⋯O2ⁱⁱⁱ	0.85	1.90	2.7215 (12)	163
O3W—H2W3⋯O7^vi	0.74	1.92	2.6424 (12)	166
C5—H5B⋯O3W^vii	0.97	2.53	3.4943 (13)	172
Symmetry codes: (i) $[x, -y+1, z-{\script{1\over 2}}]$ ; (ii) $[-x+1, y, -z+{\script{3\over 2}}]$ ; (iii) $[x, -y+1, z+{\script{1\over 2}}]$ ; (iv) x, y+1, z; (v) $[x, -y, z+{\script{1\over 2}}]$ ; (vi) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ ; (vii) x, y-1, z.

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536809054439/sj2710sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536809054439/sj2710Isup2.hkl

checkCIF report

Comment top

Citric acid or 2-hydroxy-1,2,3-propanetricarboxylic acid contains three carboxyl groups. It is found in the literature that an organism has the ability to synthesize citric acid. (Schuck, 1934; Sherman et al., 1936). Citric acid has many applications including use in the manufacture of detergents, shampoos, cosmetics and in chemical cleaning (Blair et al., 1991). It can also be used for the preparation of the catalyst LaNiO₃ for the preparation of carbon nanotubes (Jiang et al., 2007).

Guanidine can be formed by the oxidation of guanine as a final product of the protein metabolism (Raczyńska et al., 2003; Yamada et al., 2009; Sigman et al., 1993).

The asymmetric unit of title compound contains one half of a dizinc(II) complex anion, one guanidinium cation and one water solvent molecule (Fig. 1). The anion lies across a crystallographic inversion center, the other half is symmetry generated [symmetry code: 1/2 - x, 1/2 - y, 1 - z]. The Zn1 and Zn2 ions are coordinated to four O atoms from two citrate anions and two water molecules to form a distorted octahedral geometry. Two citric acid molecules are deprotonated and two guanidine molecules protonated to yield the cation and anion. The geometrical parameters of the guanidinium cations agree with those previously reported (Al-Dajani et al., 2009a,b). An intramolecular O3—H1O3···O6 hydrogen bond generates an S(6) ring motif (Bernstein et al., 1995).

In crystal structure (Fig. 2), the Zn^II complex anion and water molecules are linked into sheets parallel to the bc plane via intermoleculer O1W—H1W1···O2, O1W—H2W1···O5, O2W—H1W2···O1, O2W—H2W2···O7, O3W—H1W3···O2, O3W—H2W3···O7 and C5—H5B···O3W hydrogen bonds. The guanidinium cations are linked these sheets generating a three-dimensional framework through N—H···O hydrogen bonds (Table 1).

Related literature top

For general background to guanidine and citric acid, see: Raczyńska et al. (2003); Yamada et al. (2009); Sigman et al. (1993); Schuck (1934); Sherman et al. (1936). For applications of citric acid in industry and materials science, see: Blair et al. (1991); Jiang et al. (2007). For related guanidinium structures, see: Al-Dajani et al. (2009a,b). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Experimental top

Citric acid (anhydrous) (0.02 mol, 3.85 g) was dissolved in THF in a flat bottom flask with magnetic stirrer. In a separating funnel, guanidine carbonate (0.005 mol, 0.9 g), 99% [H₂NC(NH)NH₂].2H₂CO₃ was dissolved in THF. The guanidine solution was added in small portions to the citric acid with stirring. At room temperature, zinc chloride (ZnCl₂) (0.02 mol, 2.75 g) was added also with stirring. The reaction mixture was refluxed for 30 min. After cooling the mixture to room temperature, it was left stirring overnight. The resulting colourless crystals were filtered, washed with methanol and dried at 353 K.

Structure description top

Guanidine can be formed by the oxidation of guanine as a final product of the protein metabolism (Raczyńska et al., 2003; Yamada et al., 2009; Sigman et al., 1993).

For general background to guanidine and citric acid, see: Raczyńska et al. (2003); Yamada et al. (2009); Sigman et al. (1993); Schuck (1934); Sherman et al. (1936). For applications of citric acid in industry and materials science, see: Blair et al. (1991); Jiang et al. (2007). For related guanidinium structures, see: Al-Dajani et al. (2009a,b). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title compound with atom labels and 30% probability ellipsoids for non-H atoms. Atoms with suffix A are generated by the symmetry operation (1/2 - x, 1/2 - y, 1 - z).
	Fig. 2. The crystal packing of title compound, viewed down the c axis, showing the hydrogen-bonded (dashed lines) three-dimensional framework. Hydrogen atoms not involved in the hydrogen-bonding have been omitted for clarity.

Diguanidinium bis(µ-2-hydroxypropane-1,2,3-tricarboxylato)bis[diaquazincate(II)] dihydrate top

Crystal data top

(CH₆N₃)₂[Zn₂(C₆H₅O₇)₂(H₂O)₂]·2H₂O	F(000) = 1520
M_r = 737.21	D_x = 1.748 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 9983 reflections
a = 28.9405 (4) Å	θ = 2.5–34.8°
b = 8.5708 (1) Å	µ = 1.81 mm⁻¹
c = 11.3395 (2) Å	T = 296 K
β = 95.249 (1)°	Block, colourless
V = 2800.89 (7) Å³	0.32 × 0.30 × 0.18 mm
Z = 4

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	7693 independent reflections
Radiation source: fine-focus sealed tube	5495 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.026
φ and ω scans	θ_max = 38.3°, θ_min = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −48→50
T_min = 0.593, T_max = 0.734	k = −14→12
32332 measured reflections	l = −19→16

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.084	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.0404P)² + 0.5068P] where P = (F_o² + 2F_c²)/3
7693 reflections	(Δ/σ)_max = 0.002
190 parameters	Δρ_max = 0.45 e Å⁻³
0 restraints	Δρ_min = −0.29 e Å⁻³

Crystal data top

(CH₆N₃)₂[Zn₂(C₆H₅O₇)₂(H₂O)₂]·2H₂O	V = 2800.89 (7) Å³
M_r = 737.21	Z = 4
Monoclinic, C2/c	Mo Kα radiation
a = 28.9405 (4) Å	µ = 1.81 mm⁻¹
b = 8.5708 (1) Å	T = 296 K
c = 11.3395 (2) Å	0.32 × 0.30 × 0.18 mm
β = 95.249 (1)°

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	7693 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2005)	5495 reflections with I > 2σ(I)
T_min = 0.593, T_max = 0.734	R_int = 0.026
32332 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.031	0 restraints
wR(F²) = 0.084	H-atom parameters constrained
S = 1.05	Δρ_max = 0.45 e Å⁻³
7693 reflections	Δρ_min = −0.29 e Å⁻³
190 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Zn1	0.322092 (4)	0.394890 (14)	0.631912 (11)	0.02481 (4)
O1	0.33231 (4)	0.37163 (9)	0.45220 (8)	0.03439 (19)
O2	0.36716 (3)	0.20991 (10)	0.33603 (8)	0.03573 (18)
O3	0.31089 (3)	0.15045 (9)	0.60117 (7)	0.02494 (14)
H1O3	0.2815	0.1428	0.5651	0.037*
O4	0.39328 (3)	0.33281 (11)	0.66307 (9)	0.03675 (19)
O5	0.44700 (3)	0.16069 (13)	0.72462 (10)	0.0474 (2)
O6	0.24882 (3)	0.07623 (10)	0.42434 (9)	0.0365 (2)
O7	0.25557 (3)	−0.16794 (10)	0.36365 (10)	0.0427 (2)
C1	0.34724 (4)	0.23880 (12)	0.42612 (9)	0.02427 (18)
C2	0.34175 (3)	0.10406 (10)	0.51507 (9)	0.02214 (16)
C3	0.38848 (4)	0.06848 (13)	0.58412 (10)	0.0288 (2)
H3A	0.3844	−0.0221	0.6334	0.035*
H3B	0.4101	0.0393	0.5275	0.035*
C4	0.41101 (4)	0.19654 (14)	0.66293 (10)	0.0295 (2)
C5	0.32367 (4)	−0.04392 (12)	0.44989 (10)	0.0273 (2)
H5A	0.3410	−0.0586	0.3814	0.033*
H5B	0.3302	−0.1325	0.5020	0.033*
C6	0.27248 (4)	−0.04513 (12)	0.40863 (10)	0.02705 (19)
C7	0.45073 (5)	0.64963 (16)	0.50364 (12)	0.0382 (3)
N1	0.45132 (5)	0.61025 (16)	0.61676 (12)	0.0511 (3)
H1N1	0.4644	0.6641	0.6751	0.061*
H2N1	0.4393	0.5187	0.6424	0.061*
N2	0.47821 (5)	0.76043 (17)	0.47097 (13)	0.0552 (3)
H1N2	0.4783	0.7888	0.3966	0.066*
H2N2	0.5000	0.7945	0.5235	0.066*
N3	0.42259 (5)	0.57429 (17)	0.42351 (13)	0.0547 (3)
H1N3	0.4208	0.6209	0.3559	0.066*
H2N3	0.4020	0.5135	0.4454	0.066*
O1W	0.46013 (4)	0.85648 (15)	0.82510 (11)	0.0525 (3)
H1W1	0.4335	0.8373	0.8306	0.079*
H2W1	0.4593	0.9470	0.8020	0.079*
O2W	0.31354 (4)	0.38177 (10)	0.80498 (8)	0.0388 (2)
H1W2	0.3163	0.4610	0.8492	0.058*
H2W2	0.2975	0.3236	0.8321	0.058*
O3W	0.33513 (3)	0.63182 (9)	0.63707 (8)	0.03042 (16)
H1W3	0.3494	0.6661	0.7004	0.046*
H2W3	0.3106	0.6561	0.6328	0.046*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Zn1	0.02665 (6)	0.02218 (6)	0.02509 (7)	0.00090 (4)	−0.00047 (4)	−0.00195 (4)
O1	0.0534 (5)	0.0230 (3)	0.0269 (4)	0.0080 (3)	0.0047 (4)	0.0038 (3)
O2	0.0384 (4)	0.0412 (4)	0.0285 (4)	0.0094 (4)	0.0079 (3)	0.0043 (3)
O3	0.0251 (3)	0.0245 (3)	0.0252 (3)	−0.0002 (3)	0.0025 (3)	−0.0024 (3)
O4	0.0276 (4)	0.0324 (4)	0.0490 (5)	−0.0006 (3)	−0.0035 (3)	−0.0064 (4)
O5	0.0344 (5)	0.0509 (6)	0.0527 (6)	0.0026 (4)	−0.0192 (4)	−0.0009 (5)
O6	0.0275 (4)	0.0277 (4)	0.0521 (5)	0.0073 (3)	−0.0089 (4)	−0.0145 (4)
O7	0.0306 (4)	0.0291 (4)	0.0666 (7)	0.0027 (3)	−0.0057 (4)	−0.0205 (4)
C1	0.0243 (4)	0.0252 (4)	0.0226 (4)	0.0018 (3)	−0.0016 (3)	0.0015 (3)
C2	0.0221 (4)	0.0207 (4)	0.0231 (4)	0.0036 (3)	−0.0010 (3)	−0.0007 (3)
C3	0.0259 (5)	0.0282 (4)	0.0307 (5)	0.0052 (4)	−0.0055 (4)	0.0016 (4)
C4	0.0226 (4)	0.0355 (5)	0.0298 (5)	−0.0006 (4)	−0.0011 (4)	0.0022 (4)
C5	0.0246 (4)	0.0220 (4)	0.0345 (5)	0.0042 (3)	−0.0010 (4)	−0.0040 (4)
C6	0.0262 (4)	0.0242 (4)	0.0302 (5)	0.0032 (4)	−0.0005 (4)	−0.0051 (4)
C7	0.0341 (6)	0.0395 (6)	0.0399 (7)	−0.0022 (5)	−0.0028 (5)	0.0025 (5)
N1	0.0547 (8)	0.0579 (8)	0.0388 (7)	−0.0176 (6)	−0.0058 (6)	0.0040 (5)
N2	0.0531 (7)	0.0576 (8)	0.0534 (8)	−0.0190 (6)	−0.0043 (6)	0.0139 (6)
N3	0.0586 (8)	0.0594 (8)	0.0436 (7)	−0.0202 (7)	−0.0091 (6)	0.0033 (6)
O1W	0.0347 (5)	0.0645 (7)	0.0585 (7)	0.0026 (5)	0.0055 (5)	0.0105 (6)
O2W	0.0571 (6)	0.0320 (4)	0.0284 (4)	−0.0179 (4)	0.0093 (4)	−0.0048 (3)
O3W	0.0321 (4)	0.0257 (3)	0.0332 (4)	−0.0030 (3)	0.0009 (3)	−0.0003 (3)

Geometric parameters (Å, º) top

Zn1—O2W	2.0036 (9)	C3—H3B	0.9700
Zn1—O3W	2.0653 (8)	C5—C6	1.5123 (15)
Zn1—O1	2.0953 (9)	C5—H5A	0.9700
Zn1—O6ⁱ	2.1071 (9)	C5—H5B	0.9700
Zn1—O4	2.1259 (9)	C7—N2	1.3135 (18)
Zn1—O3	2.1436 (8)	C7—N1	1.3250 (19)
O1—C1	1.2624 (12)	C7—N3	1.3305 (18)
O2—C1	1.2430 (13)	N1—H1N1	0.8653
O3—C2	1.4382 (12)	N1—H2N1	0.9161
O3—H1O3	0.9125	N2—H1N2	0.8782
O4—C4	1.2757 (15)	N2—H2N2	0.8767
O5—C4	1.2389 (14)	N3—H1N3	0.8616
O6—C6	1.2669 (12)	N3—H2N3	0.8455
O6—Zn1ⁱ	2.1071 (9)	O1W—H1W1	0.7969
O7—C6	1.2498 (13)	O1W—H2W1	0.8189
C1—C2	1.5510 (14)	O2W—H1W2	0.8432
C2—C3	1.5302 (14)	O2W—H2W2	0.7641
C2—C5	1.5355 (14)	O3W—H1W3	0.8481
C3—C4	1.5237 (16)	O3W—H2W3	0.7377
C3—H3A	0.9700

O2W—Zn1—O3W	93.79 (3)	C2—C3—H3B	107.8
O2W—Zn1—O1	171.26 (3)	H3A—C3—H3B	107.2
O3W—Zn1—O1	94.55 (3)	O5—C4—O4	122.94 (11)
O2W—Zn1—O6ⁱ	95.68 (4)	O5—C4—C3	116.42 (11)
O3W—Zn1—O6ⁱ	93.63 (3)	O4—C4—C3	120.64 (9)
O1—Zn1—O6ⁱ	86.38 (4)	C6—C5—C2	115.82 (8)
O2W—Zn1—O4	91.59 (4)	C6—C5—H5A	108.3
O3W—Zn1—O4	94.00 (4)	C2—C5—H5A	108.3
O1—Zn1—O4	85.24 (4)	C6—C5—H5B	108.3
O6ⁱ—Zn1—O4	169.08 (3)	C2—C5—H5B	108.3
O2W—Zn1—O3	94.25 (3)	H5A—C5—H5B	107.4
O3W—Zn1—O3	171.92 (3)	O7—C6—O6	123.51 (10)
O1—Zn1—O3	77.38 (3)	O7—C6—C5	117.91 (9)
O6ⁱ—Zn1—O3	86.39 (3)	O6—C6—C5	118.54 (9)
O4—Zn1—O3	84.96 (3)	N2—C7—N1	120.18 (13)
C1—O1—Zn1	113.29 (7)	N2—C7—N3	120.45 (14)
C2—O3—Zn1	106.65 (6)	N1—C7—N3	119.36 (13)
C2—O3—H1O3	106.7	C7—N1—H1N1	124.8
Zn1—O3—H1O3	105.3	C7—N1—H2N1	123.6
C4—O4—Zn1	127.79 (7)	H1N1—N1—H2N1	111.5
C6—O6—Zn1ⁱ	125.31 (7)	C7—N2—H1N2	121.7
O2—C1—O1	124.51 (10)	C7—N2—H2N2	117.8
O2—C1—C2	117.97 (9)	H1N2—N2—H2N2	119.7
O1—C1—C2	117.48 (9)	C7—N3—H1N3	111.4
O3—C2—C3	106.41 (8)	C7—N3—H2N3	120.1
O3—C2—C5	110.47 (8)	H1N3—N3—H2N3	124.1
C3—C2—C5	109.15 (8)	H1W1—O1W—H2W1	102.7
O3—C2—C1	110.03 (7)	Zn1—O2W—H1W2	121.5
C3—C2—C1	110.05 (9)	Zn1—O2W—H2W2	124.3
C5—C2—C1	110.64 (9)	H1W2—O2W—H2W2	108.4
C4—C3—C2	117.86 (9)	Zn1—O3W—H1W3	116.0
C4—C3—H3A	107.8	Zn1—O3W—H2W3	95.9
C2—C3—H3A	107.8	H1W3—O3W—H2W3	110.5
C4—C3—H3B	107.8

O3W—Zn1—O1—C1	150.43 (8)	O1—C1—C2—O3	12.55 (13)
O6ⁱ—Zn1—O1—C1	−116.20 (9)	O2—C1—C2—C3	73.57 (12)
O4—Zn1—O1—C1	56.79 (8)	O1—C1—C2—C3	−104.39 (11)
O3—Zn1—O1—C1	−29.10 (8)	O2—C1—C2—C5	−47.13 (12)
O2W—Zn1—O3—C2	−143.52 (7)	O1—C1—C2—C5	134.91 (10)
O1—Zn1—O3—C2	33.95 (6)	O3—C2—C3—C4	−56.32 (12)
O6ⁱ—Zn1—O3—C2	121.05 (6)	C5—C2—C3—C4	−175.54 (10)
O4—Zn1—O3—C2	−52.29 (6)	C1—C2—C3—C4	62.86 (12)
O2W—Zn1—O4—C4	91.34 (10)	Zn1—O4—C4—O5	−150.02 (10)
O3W—Zn1—O4—C4	−174.75 (10)	Zn1—O4—C4—C3	30.55 (16)
O1—Zn1—O4—C4	−80.50 (10)	C2—C3—C4—O5	174.68 (11)
O6ⁱ—Zn1—O4—C4	−40.5 (3)	C2—C3—C4—O4	−5.86 (17)
O3—Zn1—O4—C4	−2.78 (10)	O3—C2—C5—C6	45.40 (12)
Zn1—O1—C1—O2	−160.08 (9)	C3—C2—C5—C6	162.07 (10)
Zn1—O1—C1—C2	17.74 (12)	C1—C2—C5—C6	−76.69 (12)
Zn1—O3—C2—C3	84.83 (8)	Zn1ⁱ—O6—C6—O7	−4.75 (18)
Zn1—O3—C2—C5	−156.82 (6)	Zn1ⁱ—O6—C6—C5	177.29 (8)
Zn1—O3—C2—C1	−34.36 (9)	C2—C5—C6—O7	−174.40 (11)
O2—C1—C2—O3	−169.49 (9)	C2—C5—C6—O6	3.68 (16)

Symmetry code: (i) −x+1/2, −y+1/2, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1O3···O6	0.91	1.87	2.6445 (13)	142
N1—H1N1···O1W	0.86	2.38	3.1607 (19)	150
N1—H2N1···O4	0.92	2.10	2.9855 (17)	161
N2—H1N2···O5ⁱⁱ	0.88	2.12	2.9351 (18)	154
N2—H2N2···O1Wⁱⁱⁱ	0.88	2.05	2.9077 (19)	166
N3—H1N3···O4ⁱⁱ	0.86	2.29	3.1011 (18)	156
N3—H1N3···O5ⁱⁱ	0.86	2.55	3.3221 (18)	150
N3—H2N3···O1	0.85	2.36	3.1788 (18)	162
O1W—H1W1···O2^iv	0.80	1.97	2.7640 (15)	177
O1W—H2W1···O5^v	0.82	2.05	2.8568 (17)	170
O2W—H1W2···O1^iv	0.84	1.88	2.7172 (12)	171
O2W—H2W2···O7^vi	0.76	1.86	2.6116 (13)	167
O3W—H1W3···O2^iv	0.85	1.90	2.7215 (12)	163
O3W—H2W3···O7ⁱ	0.74	1.92	2.6424 (12)	166
C5—H5B···O3W^vii	0.97	2.53	3.4943 (13)	172

Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) x, −y+1, z−1/2; (iii) −x+1, y, −z+3/2; (iv) x, −y+1, z+1/2; (v) x, y+1, z; (vi) x, −y, z+1/2; (vii) x, y−1, z.

Experimental details

Crystal data
Chemical formula	(CH₆N₃)₂[Zn₂(C₆H₅O₇)₂(H₂O)₂]·2H₂O
M_r	737.21
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	28.9405 (4), 8.5708 (1), 11.3395 (2)
β (°)	95.249 (1)
V (Å³)	2800.89 (7)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	1.81
Crystal size (mm)	0.32 × 0.30 × 0.18

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2005)
T_min, T_max	0.593, 0.734
No. of measured, independent and observed [I > 2σ(I)] reflections	32332, 7693, 5495
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.871

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.084, 1.05
No. of reflections	7693
No. of parameters	190
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.45, −0.29

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1O3···O6	0.9100	1.8700	2.6445 (13)	142.00
N1—H1N1···O1W	0.8600	2.3800	3.1607 (19)	150.00
N1—H2N1···O4	0.9200	2.1000	2.9855 (17)	161.00
N2—H1N2···O5ⁱ	0.8800	2.1200	2.9351 (18)	154.00
N2—H2N2···O1Wⁱⁱ	0.8800	2.0500	2.9077 (19)	166.00
N3—H1N3···O4ⁱ	0.8600	2.2900	3.1011 (18)	156.00
N3—H1N3···O5ⁱ	0.8600	2.5500	3.3221 (18)	150.00
N3—H2N3···O1	0.8500	2.3600	3.1788 (18)	162.00
O1W—H1W1···O2ⁱⁱⁱ	0.8000	1.9700	2.7640 (15)	177.00
O1W—H2W1···O5^iv	0.8200	2.0500	2.8568 (17)	170.00
O2W—H1W2···O1ⁱⁱⁱ	0.8400	1.8800	2.7172 (12)	171.00
O2W—H2W2···O7^v	0.7600	1.8600	2.6116 (13)	167.00
O3W—H1W3···O2ⁱⁱⁱ	0.8500	1.9000	2.7215 (12)	163.00
O3W—H2W3···O7^vi	0.7400	1.9200	2.6424 (12)	166.00
C5—H5B···O3W^vii	0.9700	2.5300	3.4943 (13)	172.00

Symmetry codes: (i) x, −y+1, z−1/2; (ii) −x+1, y, −z+3/2; (iii) x, −y+1, z+1/2; (iv) x, y+1, z; (v) x, −y, z+1/2; (vi) −x+1/2, −y+1/2, −z+1; (vii) x, y−1, z.

Footnotes

‡Additional correspondence author, e-mail: nornisah@usm.my.

§Thomson Reuters ResearcherID: A-5523-2009.

¶Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

HHA gratefully acknowledges funding from Universiti Sains Malaysia (USM) under the University Research Grant (No. 1001/PKIMIA/811142). HKF thanks USM for the Research University Golden Goose Grant (No. 1001/PFIZIK/811012). CSY thanks USM for the award of a USM Fellowship.

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